The Easter controversy (or Resurrection Sunday controversy) was a bitter dispute in the second and third century A.D. over the date for celebrating the Resurrection. The western (Roman) church, citing the authority of Peter and Paul, celebrated Resurrection Sunday on the Sunday following the fourteenth day of the full moon of the vernal equinox. The eastern church, citing the authority of the Apostles Philip and John, celebrated Resurrection Sunday on the fourteenth day of Nisan regardless of the day of the week.
Disagreements continued until the Council of Nicea (A.D. 325), reached a settlement for the Christian world to celebrate Resurrection Sunday on the Sunday following the fourteenth day of the paschal moon, whose fourteenth day followed the spring equinox. In A.D. 455, Pope Leo I had to resolve a lingering dispute about the date, and his decision was widely accepted.
The Roman Church then adopted a 95-year calendar for fixing the date of Resurrection Sunday, but the Celtic Church continued to use a 532-year cycle. In the ninth century the Celtic Church accepted the 95-year calendar.